define(function(require, exports, module) {
	require('jquery');

	var scrollMoveObj = null, scrollPageY = 0, scrollY = 0;
	var scrollDivList = new Array();
	// obj需要添加滚动条的对象 w滚动条宽度 className滚动条样式名称
	// obj元素 必须指定高度，并设置overflow:hidden;
	// 如要兼容IE6 必须给obj元素 指定 overflow:hidden; 
	$.fn.jsScroll = function (w, className)
	{
		/*if(typeof(obj) == 'string')	{
			//obj = document.getElementById(obj);
			obj = $(obj)[0];
		}*/
		obj = this[0];
		
		//当内容未超出现在高度时，不添加滚动条	
		if(!obj || obj.scrollHeight <= obj.clientHeight || obj.clientHeight == 0) {
			return;
		}
		obj.scrollBarWidth = w||6;
		obj.style.overflow = 'hidden';
		obj.scrollBar = document.createElement('div');
		document.body.appendChild(obj.scrollBar);
		obj.scrollBarIndex = document.createElement('div');
		obj.scrollBar.appendChild(obj.scrollBarIndex);
		obj.scrollBar.style.position = 'absolute';
		obj.scrollBarIndex.style.position = 'absolute';
		obj.scrollBar.className = className || '';
		if(!className) {
			obj.scrollBar.style.backgroundColor = '#ddd';
			obj.scrollBarIndex.style.backgroundColor = '#aaa';
		}
		
		scrollDivList.push(obj);
		scrollResetSize(obj);
		
		//使用鼠标滚轮滚动
		obj.scrollBar.scrollDiv = obj;
		obj.scrollBarIndex.scrollDiv = obj;
		obj.onmousewheel = scrollMove;
		obj.scrollBar.onmousewheel = scrollMove;
		obj.scrollBarIndex.onmousewheel = scrollMove;
		
		//拖动滚动条滚动
		obj.scrollBarIndex.onmousedown = function(evt){
			evt = evt || event;
			scrollPageY = evt.clientY;
			scrollY = this.scrollDiv.scrollTop;
			isScrollMove = true;
			document.body.onselectstart = function(){return false};
			scrollMoveObj = this.scrollDiv;
			if(this.scrollDiv.scrollBar.className == '') {
				this.scrollDiv.scrollBarIndex.style.backgroundColor = '#888';
			}
			return false;
		}
	}
	
	//当页面大小发生变化时，重新计算滚动条位置
	window.onresize = function(){
		for(var i=0; i<scrollDivList.length; i++) {
			scrollResetSize(scrollDivList[i]);
		}
	}
	
	//计算滚动条位置
	$.fn.scrollResetSize = scrollResetSize = function (o) {
		if(o.scrollHeight <= o.clientHeight) {
			o.scrollTop = 0;
			o.scrollBar.style.display = 'none';
		} else {
			o.scrollBar.style.display = 'block';
		}
		var x=0, y=0;
		var p = $(o).offset();
		x = p.left;
		y = p.top;
		/*while(p) {
			x += p.offsetLeft;
			y += p.offsetTop;
			p = p.offsetParent;
		}*/
		var borderTop = parseInt(o.style.borderTopWidth||0);
		var borderBottom = parseInt(o.style.borderBottomWidth||0);
		o.scrollBar.style.width = o.scrollBarWidth + 'px';
		o.scrollBar.style.height = o.clientHeight + 'px';
		o.scrollBar.style.top = y + borderTop + 'px';
		o.scrollBar.style.left = x + o.offsetWidth - o.scrollBarWidth + 'px';
		o.scrollBarIndex.style.width = o.scrollBarWidth + 'px';
		var h = o.clientHeight - (o.scrollHeight - o.clientHeight);
		//当滚动条滑块最小20个像素
		if(h < 20) {
			h = 20;
		}
		o.scrollBarHeight = h;
		o.scrollBarIndex.style.height = h + 'px';
		o.scrollBarIndex.style.left = '0px';
		setScrollPosition(o);
	}
	
	function setScrollPosition(o) {
		o.scrollBarIndex.style.top = (o.clientHeight - o.scrollBarHeight) * o.scrollTop / (o.scrollHeight - o.clientHeight) + 'px';
	}
	
	document.documentElement.onmousemove = function(evt){
		if(!scrollMoveObj)return;
		evt = evt || event;
		var per = (scrollMoveObj.scrollHeight - scrollMoveObj.clientHeight) / (scrollMoveObj.clientHeight - scrollMoveObj.scrollBarHeight)
		scrollMoveObj.scrollTop = scrollY - (scrollPageY - evt.clientY) * per;
		setScrollPosition(scrollMoveObj);
	}
	document.documentElement.onmouseup = function(evt){
		if(!scrollMoveObj)return;
		if(scrollMoveObj.scrollBar.className == '') {
			scrollMoveObj.scrollBarIndex.style.backgroundColor = '#aaa';
		}
		scrollMoveObj = null;
		document.body.onselectstart = function(){return true};
	}
	
	// 鼠标滚轮滚动
	function scrollMove(evt){
		var div = this.scrollDiv || this;
		if(div.scrollHeight <= div.clientHeight) return true;
		evt = evt || event;
		var step = 20;
		if(evt.wheelDelta < 0) {
			if(div.scrollTop >= (div.scrollHeight - div.clientHeight)) return true;
			div.scrollTop += step;
		} else {
			if(div.scrollTop == 0) return true;
			div.scrollTop -= step;
		}
		setScrollPosition(div);
		
		return false;
	}
});